412 The Phylogeny of the Plantar Musculature 
II. THe PLANTAR MUSCLES OF THE LACERTILIA. 
The manus of the lacertila compared with that of the urodeles showed 
a considerable increase in the number of muscle layers, the four urodelan 
layers being represented by seven. In the pes a similar increase occurs, 
but it is not carried to quite the same extent as in the manus, the flexor 
brevis medius layer being divided into only two layers instead of three. * 
In a previous paper, 04, I showed that the aponeurosis of the crural 
flexors is, in the lacertilia, divided into a superficial and a deeper layer. 
The superficial layer is continued into the planta as a well marked aponeu- 
rosis (Fig. 3, pas) intervening between the integument and the flexor 
brevis superficialis, and contains several thickened bands which pass to 
ia. 3. Transverse section through the foot of Scincus, near the bases of 
the metatarsals. ab*—abductor quinti digiti; fom, =flexor brevis medius 
str. profundum; fom, — flexor brevis medius str. superficiale; fbp, and fbp = 
fibular and tibial slips of flexor brevis profundus; fbs = flexor brevis super- 
ficialis str. superficiale; im — intermetatarsal ligaments; Jp = lateral plantar 
nerve; mp —medial plantar nerve; pa; and pa, —superficial and deep layers 
of the plantar aponeurosis. 
the digits and insert with the tendons of the flexor brevis superficialis. 
The layer is especially developed towards the fibular side of the foot, pass- 
ing in Scincus to all the digits except the first, but in Iguana being lim- 
ited to the third, fourth and fifth, only an exceedingly thin layer of fascia 
covering the muscles passing to the first and second digits. The slip to 
the minimus is a strong triangular sheet which easily separates from the 
rest of the aponeurosis. 
The flexor brevis superficialis (Fig. 3, fobs) les immediately beneath 
the superficial plantar aponeurosis and consists of a stratum superficiale 
